This invention relates to mode selective internal combustion engines providing multiple cyclic operating modes for cylinder components such as valves or pistons. U.S. Pat. No. 4,964,374 and CIP application Ser. No. 08/623,466 describe mechanisms for regulating power output of engines by alternately working cylinders between active and passive modes. Depending on load conditions, mode selective engines maintain optimum combustion conditions for a controlled number of cylinder cycles in the active mode, and eliminate combustion in remaining cylinder cycles in the passive mode. This improves the overall indicated efficiency of engines and reduces emissions of NOx and other oxides.
A large portion of indicated power of conventional engines is consumed by mechanical losses. Mode selective engines have lesser internal losses within cylinders in the passive mode because of elimination of valve movements, gas exchange and compression. Engines built as per U.S. Pat. No. 4,964,374 have no piston movements in the passive mode and thereby eliminate friction between pistons and cylinders in such passive modes. In other cases, there is reduced friction between each piston assembly and cylinder in the passive mode as unexpanded piston rings exert lesser pressure against the cylinder and unloaded pistons exert lesser pressures on gudgeon pins and the crankshaft.
With higher indicated efficiency and reduced mechanical losses, mode selective engines are brake thermally more efficient than conventional engines, particularly when passive mode cylinder operations become more frequent with lighter loads. Mode selective engines are most suited for automotive applications where engines often transmit negligible, nil or even negative power to the crankshaft over long periods, allowing simultaneous passive mode operations of all cylinders without intake of fuel and production of effluents.
Engines need good reserve power to accelerate faster even while they operate with lesser loads. The reserve power of mode selective engines is not compromised by their operations in the passive mode, as all cylinders retain the potential of delivering peak power within a few cycles by switching to the active mode. In practice, mode selective engines are operable at relatively high idling and running speeds without sacrificing fuel economy, which gives them greater reserve power than conventional engines in identical load situations.
Unfavorably, known mode selective engines are complex, large and comprise more components than conventional engines. Elaborate timing and powering mechanisms are employed for changing modes of different cylinder components.